>>> from sqlalchemy import create_engine
>>> from sqlalchemy.orm import sessionmaker
>>> engine = create_engine('postgresql://user:password@localhost/')
>>> Session = sessionmaker(bind=engine)
>>> session = Session()
>>> q = session.query(Form).filter(Form.type_id == 1)
>>> schema = {
...     'type': 'object',
...     'properties': {
...          'foo': {
...              'type': 'object',
...              'properties': {
...                  'bar': {
...                      'type': 'integer'
...                  }
...              }
...          },
...          'baz': {
...              'type': 'string'
...          }
...     }
... }

>>> from jsonalchemy import CreateJSONView
>>> create_json_view = CreateJSONView('my_view', q, Form.data, schema)
>>> session.execute(create_json_view)

>>> q = session.query(Form).filter(Form.type_id == 2)
>>> schema = {
...     'type': 'object',
...     'id_property': 'id',
...     'properties': {
...          'id': {
...              'type': 'integer'
...          },
...          'foo': {
...              'type': 'array',
...              'items': {
...                  'bar': {
...                      'type': 'integer'
...                  },
...                  'baz': {
...                      'type': 'string'
...                  }
...              }
...          },
...     }
... }
>>> create_json_view = CreateJSONView('my_view', q, Form.data, schema,
...                                   use_materialized_view=True)
>>> session.execute(create_json_view)

class CreateJSONView(sqlalchemy.schema.DDLElement):
    """
    An SQLAlchemy DDL element that constructs a standard view of JSON properties
    and creates associated partial indexes that back the view.

    Arguments:

    name -- the view name as a string
    query -- an SQLAlchemy Query indicating the table to select from and filters
    to apply
    json_column -- the SQLAlchemy Column of the table to draw data from
    json_schema -- a JSON Schema object that defines the structure of the JSON
        column
    extract_date_parts -- a list of fields corresponding to SQL timestamp
        subfields (e.g. 'year', 'month', 'day') to create as separate calculated
        columns for each datetime or date column in the JSON.  Date part columns will
        be named as <datetime_column>_year, etc.

        See
        http://www.postgresql.org/docs/8.1/static/functions-datetime.html#FUNCTIONS-DATETIME-EXTRACT
    indexes -- create indexes for the columns in the view (Default: True)
    replace -- drop the existing view with this name (Default: False)
    drop_existing_indexes -- drop existing indexes backing the view (Default: False)
    use_materialialized_view -- use a materialized instead of non-materialized
        view for intermediate views when creating an additional view of a
        JSON property containing an array of objects (Default: False)
    """
    def __init__(self, name, query, json_column, json_schema,
                 extract_date_parts=None, indexes=True, replace=False,
                 drop_existing_indexes=False, use_materialized_view=False):